1. Field of the Invention
The present invention relates to pressure sensors, more particularly phosphorescent oxygen sensors and more particularly to compositions for forming pressure sensors and coatings therefor.
2. Description of the Related Art
The field of luminescent barometry has developed as a result of continuing difficulties encountered with other mechanical means to measure pressure distributions over aerodynamic surfaces. The theories of luminescent barometry are described in detail in U.S. Pat. No. 5,359,887 and U.S. Pat. No. 5,151,603. Luminescent barometry is based on the phenomenon that some phosphorescent materials emit light at a unique wavelength and which is xe2x80x98quenchedxe2x80x99 by the presence of particular molecules such as oxygen. This quenching effect can be quantified so that the phosphorescent material, provided in an oxygen permeable matrix can be used to mere, for example, the partial pressure of oxygen passing over aerodynamic surfaces.
As a consequence of their considerable fabrication advantages, the use of polymers for the construction of sensing devices using this quenching effect is an area of intense current interest. Luminescent sensors based on composites comprising transition metal phosphorescent dyes immobilized in polymer matrices have attracted attention as oxygen sensors for both biomedical and barometric applications. Conventional phosphors dyes such as Pt (platinum) octaethylporphyrin (OEP) derivatives or RuII (ruthenium) bipyridyl (bipy) or phenanthroline (Phen) derivatives with oxygen quenchable excited states have bee dispersed in a silicone (otherwise known as polysiloxane) based polymer matrices due to their high gas permeability.
However, these conventional silicone-based polymer systems tend to be incompatible with the dyes and can lead to undesirable local concentrations and thus reduced sensitivity. Most PtOEP based systems in cross-linked silicone polymer matrices also have non-linear dependence on air pressure thereby making measurements less accurate.
More importantly, conventional polysiloxane coatings tend to continue cross-linking with time or as their temperature rises which causes irreversible changes in their phosphorescent properties as a result, making their data subject to error and generally unsuitable for measurements taken in fluctuating temperature conditions.
It is therefore an object of the present invention to provide a novel pressure sensor.
It is a further object of the present invention to provide novel compositions for pressure sensors.
It is a further object of the present invention to provide novel compositions for use as phosphorescent sensors.
It is a further object of the present invention to provide novel composition for use as phosphorescent sensors and which provide improved sensitivity, linearity, or repeatability.
In one of its aspects, the invention involves a pressure sensor comprising a stable polymer having a backbone containing nitrogen and one or more of sulfur or phosphorous, and including a phosphorescent dye agent.
Preferably, the backbone contains both phosphorous and sulfur. More preferably, the sulfur is in the form of sulfur VI, the sulfur and phosphorus have side groups selected from the group consisting of oxygen, a halogen, an aryloxy group, an alkoxy group, an arylamine group and an alkamine group.
More preferably, the sulfur has a first side group including oxygen and a second side group including a halogen.
In another preferred embodiment, the sulfur has a second side group, the phosphorous has first and second side groups which may be the same as or different from one another and from second side group on sulfur and are each selected from NHBun, OBun, OC6H4, OC6H4CF3xe2x80x94m OCH2CHxe2x95x90CH2 and OC6H4,CF3xe2x80x94p.
In another of its aspects, the present invention provides a pressure sensor comprising a stable polymer having a backbone containing nitrogen and one or more of sulfur or phosphorous, and including a phosphorescent dye agent, the polymer including therein a phosphorescent dye agent, wherein the polymer has a glass transition temperature ranging from xe2x88x9220xc2x0 C. to 0xc2x0 C. More preferably, the polymer has a glass transition temperature ranging from xe2x88x9217xc2x0 C. to 0xc2x0 C., more particularly about xe2x88x9217xc2x0 C.
In yet another aspect of the present invention, there is provided a pressure sensor comprising a stable polymer having a backbone containing nitrogen and one or more of sulfur or phosphorous, and including a phosphorescent dye agent. Preferably, the polymer and dye agent are in the form of a coating.
Preferably, pressure sensors made according to the present invention are operatively characterized by a Stern Volmer plot having a linearity ranging from 0.980 to 1.0, more preferably 0.985 to 0.995, and still more preferably 0.990 to 0.995. Alternatively, pressure sensors made according to the present invention may preferably be operatively characterized by a Stern Volmer plot having a linearity ranging from 0.989 to 0.999, still more preferably 0.996 to 0.999.
Still more preferably, pressure sensors made according to the present invention are operatively characterized by a Stern Volmer plot having one or more of the above linearity ranges and over a range of pressures, namely from about 0.1 to 75 psi more preferably 0.1 to 50 psi, still more preferably 0.2 to 40 psi.
In another aspect of the present invention, there is provided a pressure sensor comprising a stable polymer having a backbone containing nitrogen and one or more of sulfur or phosphorous, and including a phosphorescent dye agent, wherein the polymer is a first polymer block in a block copolymer. Preferably, the first polymer block includes both sulfur and phosphorous and terminates at the sulfur in an electron deficient state, and the copolymer includes a second polymer block having a backbone which includes at least one electron rich site.
Preferably, the sulfur is sulfur VI and the at least one electron rich site includes oxygen or nitrogen. More preferably, the second polymer block is formed by a ring opening polymerization of a heterocyclic group in the presence of the first polymer block and the heterocyclic group is selected from the group comprising a substituted C3-20 cycloalkyl group, a substituted C6-20 aryl group and a substituted or unbsubstituted C6-20 aralkyl group. Still more preferably, the heterocyclic group is a C3-5 cyclic group with the oxygen or nitrogen substituent therein such as tetrahydrofuran, ethylene oxide or propylene oxide.
In another aspect, the invention involves a phosphorescent oxygen sensor comprising a substrate having a surface, a polymer as define above being applied to the surface to form a coating.
In still another aspect of the present invention, there is provided a method of forming a pressure sensor, comprising the steps of:
forming a mixture including a polymer having a backbone containing nitrogen and one or more of sulfur and phosphorous, together with a phosphorescent dye agent; and
applying the mixture to a substrate.
In another of its aspects, the present invention provides a pressure sensor comprising a first stable polymer block having a backbone containing nitrogen and one or more of sulfur and phosphorous, and terminating at the sulfur in an electron deficient state, and a second polymer block having a backbone which includes at least one electron rich site, the pressure sensor further comprising a phosphorescent dye agent.
In another of its aspects, here is provided a method of fob a pressure sensor comprising the steps of:
providing a first stable polymer block having a backbone containing nitrogen and one or more of sulfur and phosphorous, and
carrying out a ring opening polymerization of an unsaturated heterocyclic group having at least one electron rich site therein, thereby to form a copolymer, and
mixing the copolymer with a phosphorescent dye agent.
Preferably, the ring opening polymerization step is carried out in the presence of the first polymer block. More preferably, the heterocyclic group is selected from the group comprising a substituted C3-20 cycloalkyl group, a substituted C6-20 aryl group and a substituted or unsubstituted C6-20 aralkyl group. Still more preferably, the heterocyclic group is a C3-5 cyclic group with the oxygen or nitrogen substituent therein. Still more preferably, the heterocyclic group is tetrahydrofuran, ethylene oxide or propylene oxide.
In still another of its aspects, the present invention provides a pressure sensor comprising a polymer of formula A, wherein:
E1, E2 and E3 are the same or are different and are selected from either sulfur or phosphorus;
R1 to R6 are either the same or different and are selected from the group comprising oxygen, a halogen, hydrogen, methyl a substituted or unsubstituted C2-20 linear or branched alkyl group, a substituted or unsubstituted C2-20 linear or branched alkenyl group, a substituted or unsubstituted C2-20 linear or branched alkynyl group, a substituted or unsubstituted C6-20 aryl group, a substituted or unsubstituted C3-20 cycloalkyl group; and
the pressure sensor further comprising a phosphorescent dye agent.
Preferable, E1 is sulfur VI and E2 and E3 are each phosphorus, each of R2 to R6 includes an oxygen or a nitrogen substituent.
More preferably, each of R3 to R6 is an aryloxy group, an arylamine group, alkoxy group or an alkamine group. Still more preferably, each of R3 to R6 is selected from the group consisting of NHBun, OBun, OC6H4, OC6H4CF3xe2x80x94m and OCH2CHxe2x95x90CH2.
The R2 is preferably a halogen or the same as or different from R3 to R6. In one embodiment, R2 and R3 to R6 are each NHBun.
In still mother of its aspects, the present invention provides a pressure sensor comprising a copolymer of the formula B wherein
E1, E2 and E3 are the same or are different and are selected from either sulfur or phosphorus;
R1 to R6 are either the same or different and are selected from the group comprising oxygen, a halogen, hydrogen, methyl a substituted or unsubstituted C2-20 linear or branched alkyl group, a substituted or unsubstituted C2-20 linear or branched alkenyl group, a substituted or unsubstituted C2-20 linear or branched aryl group, a substituted or unsubstituted C6-20 aryl group, a substituted or unsubstituted C3-20 cycloalkyl group,
R7 is selected from oxygen, nitrogen or from groups 15 and 16 of the periodic table of elements,
R8 is selected from the group comprising methylene, a substituted or unsubstituted C2-20 linear or branched alkyl group, a substituted or unsubstituted C2-20 linear or branched alkenyl group, a substituted or unsubstituted C2-20 linear or branched alkynyl group, a substituted or unsubstituted C6-20 aryl group, a substituted or unsubstituted C3-20 cycloalkyl group; and
the pressure sensor further comprising a phosphorescent dye agent.
Preferably, R7 is oxygen, nitrogen or sulfur and R3 to R6 are each selected from the group consisting of NHBun, OBun, OC6H4, OC6H4CF3xe2x80x94m, OCH2CHxe2x95x90CH2 and OC6H4CF3xe2x80x94p. Still more preferably, R2 is a halogen or is the same as R3 to R6.